webpack.config.js

const path = require('path');
const webpack = require('webpack');

process.env.NODE_ENV = process.env.NODE_ENV || 'development';

if (process.env.NODE_ENV === 'test') {
  require('dotenv').config({ path: '.env.test' });
} else if (process.env.NODE_ENV === 'development') {
  require('dotenv').config({ path: '.env.development' });
}

module.exports = (env) => {
  const isProduction = env === 'production';

  return {
    entry: ['babel-polyfill', './src/app.js'],
    output: {
      path: path.join(__dirname, 'public', 'dist'),
      filename: 'bundle.js'
    },
    module: {
      rules: [{
        loader: 'babel-loader',
        test: /\.js$/,
        exclude: /node_modules/
      }, {
        test: /\.s?css$/,
        use:  [ 'css-loader' ]
      }]
    },

    devtool: isProduction ? 'source-map' : 'inline-source-map',
    devServer: {
      contentBase: path.join(__dirname, 'public'),
      historyApiFallback: true,
      publicPath: '/dist/'
    }
  };
};